Controllable-profile roll

ABSTRACT

An improved, substantially solid core roll such as a mill roll having means for circulating heat transfer medium therethrough in close proximity to its working surface for effecting temperature control of the working surface. The improved roll includes means for independently controlling the temperature profile of the core so that the physical profile of the roll, including crowning of the roll surface, can be controlled independently from controlling the temperature of the working surface of the roll. Such improved rolls, when incorporated into an apparatus as one or both of a pair of rolls forming a nip, enable maintaining predetermined nip profiles under variable operating conditions. Such a predetermined nip profile is, for example, a nip having substantially uniform clearance throughout the length of the nip formed in the region where the working surfaces of the rolls are closest together.

limited ttes atet Maag Mar. 25, 1975 CONTROLLABLE-PROFILE ROLL [75]Inventor: Gustav A. Maag, Fort MitchelLKy.

[73] Assignee: The Proctor & Gamble Company, Cincinnati, Ohio [22]Filed: Apr. 23, 1973 [21] Appl. N0.: 353,856

[52] U.S. Cl. 165/30, 165/89 [51] int. Cl. F25b 29/00 [58] Field ofSearch 165/89, 90, 3O

[56] References Cited UNITED STATES PATENTS 2,692,118 /1954 Holloway165/90 Primary Examiner-Charles Sukalo Almrney, Agent, or Firm-Thomas J.Slone; John V. Gorman; Richard C. Witte [57] ABSTRACT An improved,substantially solid core roll such as a mill roll having means forcirculating heat transfer medium therethrough in close proximity to itsworking surface for effecting temperature control of the workingsurface. The improved roll includes means for independently controllingthe temperature profile of the core so that the physical profile of theroll, including crowning of the roll surface, can be controlledindependently from controlling the temperature of the working surface ofthe roll. Such improved rolls, when incorporated into an apparatus asone or both of a pair of rolls forming a nip, enable maintainingpredetermined nip profiles under variable operating conditions. Such apredetermined nip profile is, for example, a nip having substantiallyuniform clearance throughout the length of the nip formed in the regionwhere the working surfaces of the rolls are closest together.

5 Claims, 4 Drawing Figures 49 6| 23 re k w 42 4| 1 K 38 52 52 39 /2 33k, *2 2h 2* uc 33 K so 2% I t I I I 34 V 29l ELECTRICAL POWER PATENTEBAR 2 5 I975 sum 2 or 3 Fig. 4

DISTANCE FROM END OF ROLL, INCHES FIELD OF THE INVENTION This inventionrelates generally to providing appara tus such as mills for producingribbons of rolled sheets of coherent doughs, millable plastics, or othermaterials of the same or similar rheology, which apparatus includesnip-forming rolls having their working surfaces cooled or heated byhaving flowable heat transfer media circulated through the rolls.Specifically, the present invention relates to controlling the physicalprofile of substantially solid core rolls, substantially independentlyfrom the circulation of such flowable heat transfer media forcontrolling the surface temperature of the working surface of the roll.Such profile control is effected by independently controlling thetemperature profile of the core of the roll. By such independenttemperature control of the core and the working surface of at least oneroll, a predetermined nip profile such as one providing uniformclearance between the working surfaces of spaced rolls can be maintaineddespite variations in process variables such as pounds per lineal inchloading on the rolls. For instance, without the roll profile controlafforded by the present invention, the nip clearance would vary alongthe length of the nip as a function ofload induced bending of the millrolls.

BACKGROUND OF THE INVENTION Ideally, a pair of nip-forming rolls usedfor rolling or milling sheet or web type products such as paper, metals,plastics or dough are configured so that, when op erated, the nipclearance between such rolls is uniform throughout the axial length ofthe working surfaces of the rolls. To the degree that such nip clearanceis uniform, the products issuing from them are of uniform thicknessthroughout their entire widths. Such nips having uniform clearances areideal also for milling, grinding, or comminuting and similar physicaltreatments induced by passage between closely spaced roll surfacesbecause of the resulting uniformity of action on materials being milledby the mill rolls throughout the lengths of such nips.

Mill roll applications commonly require that the working surface of eachroll which contacts process stream materials be maintained substantiallyat a predetermined and constant temperature to avoid detrimental effectson the materials being milled.

In actual practice, however, mill roll surfaces tend to vary intemperature and are commonly distorted from their intended rightcircular cylindrical shapes while operating. Such temperature variationsand distortion are caused by varying heat and mechanical loads on theirworking surfaces resulting from variations in the materials beingmilled. For instance, varying the moisture content ofa dough mix greatlyaffects the amount of heat generated during its milling and the poundsper lineal inch loading on the mill rolls, thus affecting both rollsurface temperature control and nip clearance or nip profile control.

The prior art discloses a variety of approaches for achievingpredetermined roll or nip profiles by heating or cooling the workingsurface(s) of the roll(s) and/or by grinding the cylindrical workingsurfaces of the rolls(s) convex or concave. However, none of the discovered prior art discloses or teaches how to maintain predeterminedroll or nip profiles despite changes in roll deforming variables whilemaintaining substantially constant or predetermined temperatures on theworking surfaces of the rolls. Representative prior art US Pat. Nos.include 530,094 issued Dec. 4, 1894 to Stewart A. Davis, 737,571 issuedSept. 1, 1903 to Charles W. Bray, 2,793,006 issued May 21, 1957 to LeRoyEaby, 2,933,760 issued Apr. 26, 1960 to Elmer .I. von

der Heide, and 3,529,045 issued Sept. 15, 1970 to Nathan Rosenstein.Also, improved means for providing mill rolls having substantiallyconstant temperature or isothermal working surfaces are disclosed in thetwo commonly assigned, copending applications of Gustav A. Maag and JohnE. Callaham entitled IMPROVED MILL ROLL", Ser. No. 316,807 andSELECTIVELY INSULATED MILL ROLL", Ser. No. 316,809 (now US. Pat. No.3,834,205) which were concurrently filed Dec. 20, 1972. However, noneof'these approaches has solved, in the manner nor to the degree of theinstant invention, the problems associated with profile control of rollswhich are subjected to variable conditions such as variations in poundsper lineal inch loading of the rolls.

SUMMARY OF THE INVENTION The nature and substance of the invention willbe more readily appreciated after giving consideration to its major aimsand purposes. The principal objects of the invention are recited in theensuing paragraphs in order to provide a better appreciation of itsimportant aspects prior to describing the dletails of a preferredembodiment in later portions of the present applica tlon.

A major object of the present invention is to provide an apparatuscomprising a substantially solid-core roll and core temperature profilecontrol means so that the physical profile of the roll can be controlledsubstantially independently from the temperature of and the heat load onthe working surface of the roll.

Another major object of the present invention is providing an improved,substantially solid core roll having core temperature controlling meansfor controlling the physical profile of the roll substantiallyindependently from controlling the temperature of the working surface ofthe roll.

Another object of the present invention is providing an improved,substantially solid core, internally cooled roll having core heatingmeans for maintaining, despite variations in roll loading, apredetermined physical profile of the roll substantially independentlyfrom controlling the working surface of the roll at a constanttemperature.

Still another object of the present invention is providing an improvedapparatus comprised of at least a pair of nip-forming rolls and meansfor controlling the temperature of the working surface of at least oneroll of said pair of rolls, in which apparatus means are provided forcompensating for roll distortions substantially independently fromcontrolling the temperature of the working surface of the roll wherebythe nip formed between spaced rolls can be maintained at a substantiallyuniform clearance throughout the length of the nip during operation ofthe apparatus.

Yet still another object of the present invention is providing animproved apparatus comprising at least a pair of nip-forming rolls andmeans for controlling the temperature of the working surfaces of therolls, in

3. which apparatus means are provided for compensating for rolldistortions substantially independently from controlling the temperatureof the working surfaces of the rolls whereby the longitudinallyextending nip defining portions of the rolls can be maintainedsubstantially straight and uniformly spaced throughout the length of thenip during operation of the apparatus.

These and other objects are achieved by providing a substantiallysolid-core roll and means for controlling the temperature profile of thecore of the roll substantially independently from controlling thetemperature of the working surface of the roll so that a predeterminedphysical profile of the roll can be established and maintainedsubstantially independently from control ling the temperature of theworking surface of the roll.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes withclaims particularly pointing out and distinctly claiming the subjectmatter regarded as forming the present invention, it is believed theinvention will be better understood from the following description takenin connection with the accompanying drawings in which:

FIG. 1 is a fragmentary, partially cut away plan view of a mill assemblyembodying the instant invention.

FIG. 2 is an enlarged scale, fragmentary sectional view of the left endof the partially sectioned mill roll assembly of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of the partially sectionedmill roll assembly of FIG. 1 taken along line 33 thereof.

FIG. 4 is a composite graph of the Two Roll Total Mill Deflection vs.Distance from the end of a mill assembly like that shown in FIG. 1 undervarious specified conditions of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT A mill 19, FIG. 1, which is apreferred embodiment of the present invention is shown to include asubstantially solid core mill roll having internal passageways 55 forcirculating flowable heat transfer medium subjacent its working surface56 for controlling the temperature of working surface 56, and coretemperature profile control means 21. In the preferred embodiment mill19, core temperature profile control means 21 comprises heater 22, slipring and brush assembly 23, an electrical power controller 24,conductors 25, 26, and cable 27. Mill 19 further comprises mill roll 28which is spaced from mill roll 20 forming nip 29 of length Ltherebetween having clearance 29 at the center of the mill and clearance29" at each end. Mill rolls 20, 28 are rotatably secured to a frame forrotation by suitable drive means, which frame and drive means are notshown in FIG. 1 in order to more clearly show the essential elements ofthe present invention. Mill roll 28 may also comprise core temperatureprofile control means, but to avoid redundancy with respect to one andtwo roll embodiments of the present invention and embodiments whereinthe core temperature profile control means 21 comprises cooling meansrather than heating means, the following descriptions generally describecore temperature profile control means with respect to roll 20 only.

Briefly, core temperature profile control means 21 is provided toestablish and maintain a predetermined physical profile of roll 20substantially independently from circulating coolant through roll 20which circulating coolant is used to control the temperature of theworking surface 56 of roll 20. For instance, by applying heat to thecore 57 of roll 20 from heater 22 disposed centrally of roll 20, theroll can be crowned or made somewhat barrel shape even though, be beinginternally cooled, it has a substantially isothermal working surface.Such controllable crowning is effective for compensating for rolldistortions such as bending induced by milling forces. By suchdistortion compensation of either roll, a nip formed between adjacentrolls can be maintained so that the nip has a substantially uniformclearance throughout its length despite variations in milling inducedbending forces and heating. Further, by such distortion compensation ofboth rolls of an apparatus comprising at least one pair of nipformingrolls, the longitudinally extending nip defining portions of the rollscan be maintained substantially straight and uniformly spaced throughoutthe length of the nip during operation of the apparatus despitevariations in milling induced distortion of the rolls.

Roll 20, FIG. 1, comprises cylinder 30, closure collars 31, 32, two eachgaskets 33, 34, bushings 35, 36, a plurality of rods 37, coolantcouplings 38, 39, tube 40, seal 41, cap 42, and spacer 43.

Cylinder 30, FIGS. 1-3, is substantially solid and includes integraljournals 48, 49, and shoulders 50. Each journal is bored axially toprovide a coolant manifold 52. Each end of cylinder 30 is provided witha plurality of radially extending holes 53 intermediate shoulder andmanifold 52. Cylinder 30 also is provided with an axially extendingcavity 54 through its center for accommodating heater 22 and forenabling installation and removal of heater 22. Cavity 54 is configured,with respect to the configuration of heater 22, to provide intimatecontact with heater 22 when installed therein so that there is a goodheat transfer path from heater 22 to cylinder 30.

Cylinder 30 of the preferred embodiment of the present invention also isprovided, with a plurality of circumferentially spaced, longitudinallyextending coolant passageways 55 subjacent its cylindrical workingsurface 56.

Cylinder 30, closure collars 31, 32, gaskets 33, 34, bushings 35, 36 androds 37 are assembled to form roll 20 in such a manner that coolant canbe circulated through roll 20 by entering journal 48, then passingradially outwardly through one set of holes 53, then passinglongitudinally of cylinder 30 through passageways 55 subjacent workingsurface 56, then passing radially inwardly through the second set ofholes 53, and then exiting through journal 49. Alternatively, the flowpath could be the reverse of this sequence. In this manner, the coreportion 57 (hereafter core 57) of cylinder 30 is virtually enveloped bya sheath of coolant during mill operation. Such a roll assembly isdisclosed in the hereinbefore referenced, commonly assigned, copendingpatent applications, Ser. No. 316,807 now abandoned and Ser. No. 316,809(now US. Pat. No. 3,834,205).

Tube 40, rotary seal 41, and cap 42 are adapted to sealheater-accommodating cavity 54 from coolant passing through manifolds 52in journals 48, 49. Couplings 38, 39 are provided with suitable seals tocomplete the assembly of mill roll 20 so that, when roll 20 is rotatablymounted and driven (by means not shown coolant can enter throughcoupling 38 as indicated by arrow 60 and exit through coupling 39 asindicated by arrow 61 or the reverse thereof.

Heater 22 of the preferred embodiment of the present invention is abouthalf the length L of the working surface of roll 20. Heater 22 iselectrically powered, has a tubular shape and is installed in cavity 54of cylinder 30 so that it is symmetrically disposed with respect toworking surface 56. Spacer 43, which may be an integral part of cap 42,is provided so that heater 22 is properly positioned in cavity 54 whenthe right end of heater 22 abuts the left end of spacer 43.

Referring to FIGS. 1 and 2, electrical power is applied to heater 22through power controller 24, conductors 25, 26, slip ring and brushassembly 23 and cable 27.

Slip ring and brush assembly 23 provides the necessary electricalconnections between the stationary elements (i.e., power controller 24,and conductorsv 25, 26) of the core temperature profile control means21, and cable 27 and heater 22 which rotate with roll 20.

In the preferred embodiment of the present invention, power controller24, which is amenable to being incorporated in an automatic controlscheme, is pro vided to enable adjusting, as necessary, the electricalpower delivered to heater 22 in order to maintain a uniform clearance ofnip 29 throughout its length L to compensate for changes in thedistortion of mill roll 20 precipitated by milling variables.

In operation, coolant is conducted through mill roll 20 at a fast enoughrate to maintain working surface 56 substantially isothermally at apredetermined temperature which temperature is dependent on theproperties of the material being milled. Then, substantiallyindependently from the rate of coolant flow or the heat flux betweenworking surface 56 and the walls of coolant passageways 55, powercontroller 24 is adjusted to increase or decrease the heating of core 57to accentuate or reduce respectively the crown of roll 20 as necessaryto compensate for variations in mill roll distortion. In this manner,the clearance ofnip 29 can be maintained substantially uniformthroughout its length L despite milling variations.

For instance, if the moisture content of a potato flour dough mix isreduced, such reduction precipitates an increase in the pounds perlineal inch loading on rolls 20, 28. Such increased loading bends therolls so that the clearance 29 at the center of nip 29 becomes greaterthan the clearance 29" at the ends of nip 20. Thus, nip 29 becomessomewhat double convex in longitudinal cross section. To compensate forsuch distortion of nip 29, power controller 24 is adjusted to increasethe power delivered to heater 22 to sufficiently heat core 57 until roll20 becomes sufficiently crowned to offset the load induced bending ofboth rolls 20 and 28 whereupon the clearance of nip 29 is restored to asubstantially uniform state.

By also providing core temperature profile control means for roll 28,the amount of compensation required can be divided between rolls 20 and28. If core temperature profile control means is provided for bothrolls, the nip therebetween can be maintained with a substantiallyrectangular longitudinal cross section whereas, if core temperatureprofile control is provided for only one roll of a pair of nip-formingrolls, the nip therebetween may, under some conditions, have an arcuatelongitudinal cross section. Although nips having either arcuate orrectangular longitudinal cross sections or clearances are believedsuitable for plastic or flexible materials such as ribbons of rolledsheets of coherent dough, it is believed that rectangular longitudinalnip cross sections are more suitable for apparatus for processing,forwarding, or drawing materials such as metals and glass.

Referring now to FIG. 4, the curves, which are discussed below,illustrate the effectiveness of the present invention for controllingthe crown of a mill roll so that a sheet of dough issuing therefrom isof substantially uniform thickness across its full width. Such uniformthickness. of a sheet is beneficial because, for instance, it improvesthe uniformity of articles produced therefrom.

The mill from which the data for the curves of FIG. 4 were obtainedcomprises two rolls comprising right circular cylinders like cylinder 30approximately twenty-five inches in diameter having a working surfaceabout forty-one-and-one-half inches long which cylinders are fabricatedof AISI-4340I-I (steel) forgings. One of the rolls comprises a centrallydisposed heater 22 having a three-quarter inch diameter and a twentyinch length, which heater 22 is rated to dissipate a maximum ofthirty-three hundred watts. When the data for FIG. 4 was obtained, themill was operated to produce a sheet of potato-flour dough having anominal thickness of ten-thousandths of an inch with four-thousandpounds per lineal inch loading.

Curve 101 shows the theoretical combined deflection of the mill rollswhich is the change in the clearance of nip 29 under four-thousandpounds per lineal inch loading. This loading would cause clearance 29'at the center of the nip to be about one-thousandth of an inch greaterthan clearance 29 at the ends of the nip. Although the absolutemagnitude of such deflection is small in a forty-inch mill, thevariation in nip clearance is a not insignificant ten percent of anominal ten mill nip clearance.

Curve 102 shows the actual total change in nip clearance or deflection,without core heating, of the mill rolls under actual operatingconditions with a heat load of about fifty-thousand to aboutsixty-thousand BTU per hour. The curve reflects the combination ofthermal and mechanical distortion.

Curve 103 shows the compensating effect on the clearance of nip 29resulting from heating the core 57 of one roll with a heater 22dissipating about fifteenhundred watts.

Curve 104 represents the net effect of curves 102 and 103 which showsthat core heating substantially compensates for the thermally andmechanically induced roll distortions shown by curve 102.

As previously stated, loading on rolls of dough mills is greatlyaffected by changes in moisture content of the dough mix. Were themoisture content of the dough mix increased above the level prevailingwhen the data for FIG. 4 were taken, curves 101 and 102 would reflectless distortion which in turn would require less heater power forcompensation, and vice versa.

Although it would be theoretically possible to grind aone-half-thousandths of an inch crown in both rolls, or alternatively aone-thousandths of an inch crown in one roll to provide a mill having :auniform clearance nip under the conditions stated above, such machiningis difficult and expensive. Moreover, such an approach would provide auniform clearance nip at essentially only one constant value of loadingand heating. It

would not provide variable and controllable compensation means formaintaining a substantially uniform clearance nip over a range oftransient operating conditions as is provided by the present invention.

Although the preferred embodiment of the present invention describedherein comprises a mill roll, it is not intended to thereby foreclosecalender rolls, and other single or two roll apparatuses from the scopeof the present invention. Also, although the preferred embodimentcomprises a single cylindrical-shape electrical heater 22 disposedcentrally of core 57 and extending axially thereof in order to achieve avariable crown roll profile, other roll or nip profiles are achievablethrough the use of the present invention as by distribut ing a pluralityof controllable heaters or coolers through roll and independentlycontrolling them to establish the required core temperature profile.

While particular embodiments of the present invention have beenillustrated and described, it will be obvious to those skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope of the invention. It is intended to cover inthe appended claims all such changes and modifications that are withinthe scope of the invention.

What is claimed is:

1. In an apparatus comprising a rotatably mounted substantiallysolid-core roll having a cylindrical working surface and means forcontrolling the temperature of said working surface, the improvementcomprising means for controlling the temperature profile of the core ofthe roll substantially independently from controlling the temperature ofsaid working surface, said means for controlling the temperature profilebeing dis posed radially inwardly from said working surface and saidmeans for controlling the temperature of said working surface wherebythe physical profile of the roll can be controlled substantiallyindependently from the temperature of and the heat load on the workingsurface of the roll.

2. In an improved, substantially solid-core, roll having passageways forflowable heat transfer media disposed subjacent the working surface ofthe roll and means for circulating flowable heat transfer media throughsaid passageways to control the temperature of said working surface, theimprovement comprising core temperature profile control means disposedradially inwardly from said passageways for establishing and maintaininga predetermined physical profile of said roll substantiallyindependently from circulating flowable heat transfer media through saidpassageways.

3. In an improved, substantially solid-core roll having passageways forflowable heat transfer media disposed subjacent the working surface ofthe roll and means for circulating flowable heat transfer media throughsaid passageways to control the temperature of said working surface, theimprovement comprising core temperature profile control means forestablishing and maintaining a predetermined physical profile of saidroll substantially independently from circulating flowable heat transfermedia through said pasageways, said core temperature profile controlmeans comprising heating means disposed centrally of said core and meansfor varying the heat output from said heating means.

4. In an improved, substantially solid-core roll having passageways forflowable heat transfer media disposed subjacent the working surface ofthe roll and means for circulating flowable heat transfer media throughsaid passageways to control the temperature of said working surface, theimprovement comprising core temperature profile control means forestablishing and maintaining a predetermined physical profile of saidroll substantially independently from circulating flowable heat transfermedia through said passageways, said core temperature profile controlmeans comprising a tubular electric heating element extending axially ofsaid roll and means for varying the electrical power dissipated by saidelement.

5. The improved roll of claim 4 wherein said heating element extendsaxially about one-half the axial length

1. In an apparatus comprising a rotatably mounted substantiallysolid-core roll having a cylindrical working surface and means forcontrolling the temperature of said working surface, the improvementcomprising means for controlling the temperature profile of the core ofthe roll substantially independently from controlling the temperature ofsaid working surface, said means for controlling the temperature profilebeing disposed radially inwardly from said working surface and saidmeans for controlling the temperature of said working surface wherebythe physical profile of the roll can be controlled substantiallyindependently from the temperature of and the heat load on the workingsurface of the roll.
 2. In an improved, substantially solid-core, rollhaving passageways for flowable heat transfer media disposed subjacentthe working surface of the roll and means for circulating flowable heattransfer media through said passageways to control the temperature ofsaid working surface, the improvement comprising core temperatureprofile control means disposed radially inwardly from said passagewaysfor establishing and maintaining a predetermined physical profile ofsaid roll substantially independently from circulating flowable heattransfer media through said passageways.
 3. In an improved,substantially solid-core roll having passageways for flowable heattransfer media disposed subjacent the working surface of the roll andmeans for circulating flowable heat transfer media through saidpassageways to control the temperature of said working surface, theimprovement comprising core temperature profile control means forestablishing and maintaining a predetermined physical profile of saidroll substantially independently from circulating flowable heat transfermedia through said pasageways, said core temperature profile controlmeans comprising heating means disposed centrally of said core and meansfor varying the heat output from said heating means.
 4. In an improved,substantially solid-core roll having passageways for flowable heattransfer media disposed subjacent the working surface of the roll andmeans for circulating flowable heat transfer media through saidpassageways to control the temperature of said working surface, theimprovement comprising core temperature profile control means forestablishing and maintaining a predetermined physical profile of saidroll substantially independently from circulating flowable heat transfermedia through said passageways, said core temperature profile controlmeans comprising a tubular electric heating element extending axially ofsaid roll and means for varying the electrical power dissipated by saidelement.
 5. The improved roll of claim 4 wherein said heating elementextends axially about one-half the axial length of said core.